This invention relates to the manufacture of articles by the technique known variously as squeeze forming, squeeze casting or extrusion casting which, for the sake of convenience, throughout this specification the claims will be referred to as "squeeze forming". Basically the technique of squeeze forming comprises introducing liquid metal into a first part of a mould, closing the mould under pressure so that the liquid metal is displaced by the mould closure to fill a cavity within the mould without entrapping air, maintaining the metal under pressure whilst solidification takes place so as to ensure that any shrinkage cavities which may form are closed and filled, and then opening the mould and removing the formed article.
Metals most conveniently employed to produce squeeze formed articles are aluminium and aluminium alloys and although such squeeze formed aluminium or aluminium alloy articles are of sound metallurgical structure and strength, they can sometimes be subject to unacceptably severe wear conditions. For example, a support wheel for a track-laying vehicle of the type described in European Patent Application 79,300,842.6 (published as No. 0,005,937) is produceable by squeeze forming in aluminium or aluminium alloy but that part of the wheel which is engaged by the steel horns of the track is subject to extreme wear conditions.
It will be understood that many differing squeeze formed articles can be subject to severe wear conditions, and it is an object of the present invention to provide a squeeze formed article, and method of producing such article, wherein wear-resistant means are incorporated.